In the last few years, carbon dioxide (CO2) made a come-back in refrigeration applications where it is used as a refrigerant fluid or coolant. This is mainly due to the concerns regarding the effects of refrigerants on ozone layer depletion and global warming. CO2 is known as a naturally available, safe, environmental friendly refrigerant with good thermo-physical and transport properties.
In cooling systems, most of the energy costs come from the motors that drive compressors, fans, and pumps. There is thus a need to reduce the energy consumption in cooling systems while using CO2 as an environmental friendly refrigerant.